CD4 and inflammatory bowel disease: We speculated that the cause of this result might be the increase of serum CXCL13 in IBD patients, which promoted CD4+CXCR5+ T cells homing to the follicular area of lymph nodes, significantly decreased the percentage of CD4+CXCR5+ T cells in peripheral blood circulation, and eventually lead to an increase in inhibitory CD19+CD5+ B cells and thereby enhancing humoral immunity (Figure 2C).